A patient with an acute bleed is most accurately described as having which type of acute kidney injury?

A patient with an acute bleed is most accurately described as having which type of acute kidney injury?

• A. Prerenal acute kidney injury
• B. Renal acute kidney injury
• C. Postrenal acute kidney injury
• D. None of the above apply

Answer: (A)

Prerenal acute kidney injury is the right description here because the problem lies before the kidneys—in this case, reduced blood flow from acute blood loss. Losing a significant amount of blood lowers circulating volume and effective arterial blood pressure, which drops renal perfusion and GFR. The kidneys respond by conserving water and sodium to maintain blood pressure and perfusion, so the tubular function remains intact even though filtration falls. This pattern gives clues such as a high BUN-to-creatinine ratio and often a low fractional excretion of sodium, reflecting preserved tubular reabsorption in the setting of reduced perfusion. If fluids are given and perfusion improves, kidney function typically recovers quickly, which is characteristic of prerenal injury. By contrast, intrinsic renal injury would involve actual damage to kidney tissue with different urine and lab findings, and postrenal injury would be due to obstruction rather than decreased perfusion.

Prerenal acute kidney injury is the right description here because the problem lies before the kidneys—in this case, reduced blood flow from acute blood loss. Losing a significant amount of blood lowers circulating volume and effective arterial blood pressure, which drops renal perfusion and GFR. The kidneys respond by conserving water and sodium to maintain blood pressure and perfusion, so the tubular function remains intact even though filtration falls. This pattern gives clues such as a high BUN-to-creatinine ratio and often a low fractional excretion of sodium, reflecting preserved tubular reabsorption in the setting of reduced perfusion. If fluids are given and perfusion improves, kidney function typically recovers quickly, which is characteristic of prerenal injury. By contrast, intrinsic renal injury would involve actual damage to kidney tissue with different urine and lab findings, and postrenal injury would be due to obstruction rather than decreased perfusion.